South Downs Planetarium

Easter full moon

30th March 2018, 15:30 – 16:30

The Moon is our nearest neighbour, and many people do not realise what a fascinating world it is. Its phases are also linked to the date of Easter, although not in a simple way!

The commonly stated rule that Easter is the first Sunday after the first Full Moon following the vernal or spring equinox is not quite correct. Strictly speaking, these days, Easter is the first Sunday following the “Ecclesiastical Full Moon” date after March 20th. Rather confusingly, the date of the Ecclesiastical Full Moon is determined from tables, and it may differ from the date of the real Full Moon by up to two days. This is because in June 325 AD, astronomers decided to approximate the true full moon dates for the Christian church, calling them Ecclesiastical Full Moons. Incidentally, March 20th was the date of the equinox in 325 AD.